A tricycle is often preferred over other vehicles such as bicycles due to its stability. Owing to its two rear wheels, a tricycle is very stable, and the risk of falling over with a tricycle is minimal. This is very useful especially in a stationary position, when not operating the tricycle, for example when stopped at a red light, since one does not have to get off the tricycle or place a foot on the road on which the tricycle is being operated.
There are, however, disadvantages associated with tricycles. When storing the tricycle, it is important that the tricycle does not take up much space. For storage purposes, it is desirable that the length and the width are as small as possible. When the tricycle is being used, thus when riding the tricycle, the two rear wheels are arranged laterally on opposite sides with respect to the longitudinal axis of the tricycle. The greater the distance/space between the rear wheels in the widthwise direction of the tricycle, the greater the stability of the tricycle. In the majority of tricycles, the space between the rear wheels and the space between the front wheel and the rear wheels, and thus the width and length of the tricycle, are not adjustable. A tricycle having a certain length thus occupies more space than a bicycle of said same length because a bicycle has a single rear wheel, and therefore the width of the bicycle is less than the width of the tricycle.
A solution to this storage problem is described in document EP 1937541. Document EP 1937541 discloses a folding tricycle comprising a front wheel, two rear wheels and a folding frame. The advantage of a folding frame is that the dimensions of the frame and therefore the tricycle can be adjusted. It is therefore possible to reduce the dimensions when storing the tricycle. The frame comprises two arms, and each arm carries a rear wheel. Each arm is connected to the rest of the frame in order to able to assume at least two positions. In a first position, the position of use, if the tricycle is driven, the distance between the two rear wheels and the distance between the front wheel and two rear wheels is maximum, the dimensions, the length and the width, of the tricycle are thus maximum. This enhances the stability of the tricycle. In a second position, the storage position, the distance between the two rear wheels and the distance between the front wheel and two rear wheels is minimal, therefore the dimensions of the tricycle are minimal. The drawback of this tricycle is that the tricycle cannot be driven or that it is impossible to roll when it is in the storage position. In a storage space, it is often necessary to move the tricycle to the desired location while the tricycle is in its storage position. For the tricycle described in EP 197541, this proves to be difficult because one must lift or drag the tricycle. This manoeuvre is very difficult with a slightly heavier tricycle.
In some instances it is desirable that the width of the tricycle be smaller during operation. In narrow passageways or in heavy traffic, it is often desirable that there is not much space between the rear wheels. If the rear wheels are closer together, the tricycle can be used in narrow passageways and in heavy traffic. Nevertheless, for the tricycle described in EP 1937541, if the distance between the rear wheels is reduced, it is no longer possible to ride the tricycle.
Other solutions to the problem of storing tricycles are described in documents US 2009/0115168 and DE 20 2011 002 811. However, these tricycles are not suitable for transporting a person, and in their storage position they no longer rest on their three wheels. Thus, they can no longer be used as a tricycle in their storage position. The tricycle described in US 2009/0224495 also solves the problem of storage, but this tricycle is not adapted to transport a person and in its storage position it is no longer able to perform its function, that of transporting a load.
The width of the tricycles described in documents US 2008/0001374 and US 2007/017066 is adjustable. However, if the width decreases, the length increases, and vice versa such that they do not truly have a compact position and the problem of storage still remains.